The U.S. Environmental Protection Agency (EPA) recently released its annual greenhouse gas (GHG) inventory report. Using new data and information, the EPA lowered its estimate of fugitive methane emissions from natural gas development by 33 percent, from 10.3 million metric tons (MMT) in 2010 to 6.9 MMT in 2011. While such a reduction, if confirmed by measurement data, would undeniably be a welcome development, it doesn’t mean that the problem is solved.

Here are five big reasons we should care about fugitive methane emissions:

1) Emissions Are Still Too High.

Methane is a potent greenhouse gas and a key driver of global warming. Methane is 25 times stronger than carbon dioxide over a 100-year time period and 72 times stronger over a 20-year period. In fact, 6.9 MMt of methane is equivalent in impact to 172 MMt of CO2 over a 100-year time horizon. That’s greater than all the direct and indirect GHG emissions from iron and steel, cement, and aluminum manufacturing combined. Reducing methane emissions is an essential step toward reducingU.S. greenhouse gas emissions and slowing the rate of global warming.

Even with the drop in EPA’s estimate of emissions from natural gas systems, the average fugitive methane leakage rate is still above 1 percent (see text box). Previous research has shown a 1 percent leakage rate to be an important benchmark: Below this rate, switching from diesel to natural gas as fuel for buses and long-haul trucks produces climate benefits over any time horizon. (The equivalent leakage rate for switching from coal to natural gas for electricity generation is roughly 3.2 percent.) It’s important to note that these rates are only benchmarks—not goals. The goal should be to reduce fugitive methane emissions by as much as is technologically and economically feasible.

2) Natural Gas Should Be Cleaner.

Natural gas comprised 29 percent of the U.S. electricity mix in 2012 and is widely used for industrial processes and for residential cooking and heating. The Energy Information Administration projects a significant expansion in natural gas production over the coming decades, increasing by more than 40 percent between 2012 and 2040, with much of that coming from shale and other unconventional sources. WRI analysis has found that for the United States to meet its stated goal of reducing GHG emissions 17 percent below 2005 levels by 2020–to say nothing of the deeper cuts needed beyond 2020–it needs to reduce fugitive methane emissions from natural gas.

EPA currently has the authority to set standards for greenhouse gas emissions under the Clean Air Act. The agency’s recent rules aimed at reducing volatile organic compounds (VOCs) and hazardous air pollutants had the added bonus of indirectly reducing methane emissions. Going forward, the agency should set standards that address methane emissions directly, in order to maximize GHG reductions. States also have the ability to demonstrate policy leadership and limit fugitive methane emissions from natural gas production.

5) Emissions Are Still Uncertain.

Upstream GHG emissions from natural gas systems are notoriously difficult to quantify, with many diffuse sources of emissions and scarce measurement data, complicated by the fact that the industry is rapidly expanding and transforming. EPA’s GHG Inventory is the best peer-reviewed data source currently available. However, it still relies heavily on industry-supplied emissions factors and activity data as opposed to independently verified, direct measurements. Plus, the dramatic drop in emissions estimates is attributed almost entirely to a change in EPA’s estimate of methane emissions associated with liquids unloading operations—just one part of the entire natural gas production process. The agency’s primary data source for liquids unloading is a recent industry survey.

More and better measurement data from all stages of the natural gas lifecycle will go a long way toward alleviating uncertainty around the magnitude of fugitive methane emissions. Several studies are underway that will help in this regard. But with more than half a million natural gas wells, hundreds of thousands of miles of pipeline, and thousands of processing plants and compressor stations – plus the huge amount of variation between individual producers – we will never have perfect data. But we know enough to take action to start reducing methane emissions now.

While the EPA’s new data is encouraging, the fugitive methane problem is far from solved. Meanwhile, without policy action, greenhouse gas emissions will continue to rise, and climate change’s impacts continue to be felt. We cannot afford to take a wait-and-see approach. Fugitive methane emissions should be reduced as much and as quickly as possible.

UPCOMING CONGRESSIONAL TESTIMONY: WRI’s Senior Associate, James Bardbury, will testify before the U.S. House of Representatives Energy and Commerce Subcommittee on Energy and Power this Tuesday, May 7th. Learn more about the testimony, “U.S. Energy Abundance: Exports and the Changing Global Energy Landscape.”

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